Acoustic device



Patented-Apr. 16, 1929.

l UNITED STATES PATENT OFFICE.

CHARLES L. GOODRM, F NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COM- NEW YORK, N. Y., A

CORPORATION OF NEW YORK.l

ACOUSTIC Janvier;

Application med september 22, 1921.

This invention relates to acoustic devices. One of the objects of the invention is the provision of a very light and stiff acoustic diaphragm.' i This invention relates to acoustic devices and more particularly to diaphragms for use iiisuch devices.

The object ofthe invention in general is to provide a iight relatively stiff diaphragm, the movement of which in response to vibrations will be approximately the saine at any point on its surface thereby simulating that of a piston.

In order to obtain a diaphragm in which the movement throughout the whole area will Q be approximately equal in response to sound vibrations, or in the production of such vibrations, it has heretofore been the practice to make them relatively thick at the center portion and gradually tapering toward the .peripheral portion. Such diaphragms are usually constructed by co-axially superimposing a plurality of layers of material of different' diameters. The improved results thus obtained, as compared with a simple diaphragm of uniform thickness due to in- Vcreased stiii'ness,

at least, by the increased weight.

In accordance with the general features of 3o this invention there is provided a hollow dia hragm so constructed that use may be ma e of very light material. In its preferred form the diaphragm consists of two dished surfaces, formed of a light and com paratively stili material and secured together to form a hollow body having a double convex surface, the opposing sections serving to mutuall reenforce and stilien each other in the irection of the applied vibration.

tive view, partly machine sound both features of in cross section, of a talkin` ox in which are incorporate .the invention.

material, such as corlr, is insertedv between the members 1, and is clamped in place by the small bolt 3. After the diaphragm is are preferably secured is oli'set, to some extent" The accompanying drawing is a perspec.

The acoustic diaphragm is here shown in f which comprises two Serial N 0. 502,425.

assembled its outer surfaces are varnished and it is againsubjected to heat treatment.

The peripheral portions of the diaphragm together as shown.

he diaphragm is shown mounted between a pair of pneumatic tubes suitable means may be employed. e Such a diaphragm is obviously of very light weight as compared with a solid structure of equal dimensions, and the members 1, although they are very thin, are capable of withstanding considerable lateral stress without appreciable distortion, due to the dished formation. A movement of the diaphragm in response to sound vibrations in the important audible range, or in the lproduction of sound vibrations in the important audible range, simulates very closely the movement of the piston. The effect of the added stiffness due to the particular shape used is to shift the lowest resonant frequency to the higher parts of the audio range of frequencies where the damping is normally much greater, thereby reducing tone distortion to a minimum.

The stylus bar 5 is attached to the bolt 3 and is thereby capable of'transmitting to the diaphragm the vibrations imparted to the stylus 6 by therecord 7. The stylus bar 5 is pivoted on the knife edge 8, which is carried by the sound box member 9, and is propreferably of rubber, which in the stance are shown as spherical in s Although the invention as illustrated is applied to a reproducer, it is understood that it is equally applicable to all acoustic devices employing diaphragms.

hat is claimed is:

1. A hollow acoustic diaphragm comprising two initially dished members and a Spacer of fixed length therebetween disposed at the center portions of said members.

2. A hollow acoustic diaphragm com prising two initially dished members secured together at their peripheral portions and separated at their center portions thereby forming a closedchamber.

3. A hollow acoustic diaphragm compris ing two initially dished members secured together at their peripheral portions and present inape.

separated-a constant distance at their center portions, and a spacer-of fixed length disposed between said members.

4. A diaphragm for anv acoustical device comprising a pair of initially dished members secured together at their peripheries with their hollow sides facing each other,

and forming a closed rigid structure capable of Vibrating as a'unit.

5. As an article of manufacture, a diaphragm construction forreproducers consisting of two similarly formed conical diaphragms outwardly flanged at their peripheries and secured together to provide an enclosed compartment therebetween without sound openings therein.

G. As an article of manufacture, a diaphragm for sound reproduccrs consisting ot' two circular members of sheet material having central depressions therein and juxtaposed with their peripheral portions in contact and their central portions separated, and 4 means supported by said members for securing them together to form a closed hollow acoustic chamber.

7. As an article of manufacture, a diaphragm for sound reproducers consisting of two circular members having depressed -central portions juxtaposed with their peripheral portions in Contact, a separator between the central portions `and means extending through said members and said separator to' secure said members together to form a closed hollow chamber.

8. As an article of manufacture, a diaphragm for sound reproducers consisting of two conical members, means independent of any diaphragm mounting, :tor securing said members together with their peripheral portions in contact and their aipices separated to form a closed hollow chamber.

9. As an article of manufacture, a dia- :messes phragm for sound reproducers consisting of two conical members juxtaposed with their [peripheral portions in contact and their apices separated and :tacing in opposite directions, and means through the center of said members for securing them together to` form a closed hollow chamber.

lO. its an article'of manufacture, a dia- `phragm for sound reproducers consisting of two sheets of thin and inherent-ly stift' material having central depressions juxtaposed with their depressed portions facing in opposite directions and separated and their peripheral portions in contact, and means holding said sheets in said relation to forni a closed hollow chamber, said means forming a part ot said diaphragm.

l1. As an article ot manufacture, a diaphragm it'or sound reproducers comprising two conical members et sheet material outwardly flanged at their peripheries and juxtaposed with their ilanges together to Ylorm a closed hollow acoustic chamber, and means forming a part of said diaphragm for holding said members together.

l2. As an article ot' manufacture a diaphragm consisting of two sheets ol' thin material in conical form, said sheets being juxtaposed with their peripheral portions together to mutually r inforce each other and t'orm a closed hollow chamber, and means tor holding said members in said relation, said `means being part ot' said diaphragm.

ln witness whereof, :l hereunto subscribe my name this 20th day ot September, D. 1921.

CHARLES L. GUODRUM.

therein.A 

